US2504209A - Reversing propeller control - Google Patents

Description

April 18, 1950 E. MARTIN Erm. 2,504,209

REVERSING PROPELLER CONTROL Filed Jan. l0, 1944 Erle at' 111.

ATTORNEY Patented Apr. 18, 1950 orifice imvEaslNG PROPELLER coN'rnoL lErle Martin, West Hartford, Conn., and Murray C. Beebe, Jr., Altadena, Calif., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation oi' Delaware Application January 10, i944, Serial No. 517,686

23 Claims.` (C11. 170-i60.19)

This invention relates to control mechanism and more particularly to a control for a reversible propeller.

An object of the invention is to control automatically a propeller in its reverse position as well as in its forward position.

A further object is to maintain a constant speed of the propeller in both its forward and vreverse positions.

A still further object is to provide mechanism for automatically changing the governor connections so that a single governor may control the propeller in both its forward and reverse positions.

Other objects and advantages will be apparent from the speciiication and claims, and from the accompanying drawing which illustrates what is now considered to be a preferred embodiment of the invention.

In the drawing:

Fig. 1 is a partially schematic vertical section through the governor and the control mechanism.

Fig. 2 is a schematic elevation of the propeller showing the connection of the control mechanism therewith.

Fig. 3 is a detail showing the pitch changing mechanism in contact with the low pitch stop.

Fig. 4 is a detail showing the pitch changing mechanism in reverse pitch position, and

Fig. 5 is a modification showing electrical means for operating the reversing valve.

Referring to Fig. 2, this invention relates to the control of Aa reversible pitch propeller generally indicated at Ill having a pitch changing rod I2 which has a denite and diterent position for each propeller pitch position. Although this invention is applicable to any propeller having a pitch changing mechanism positioned in accordance with the propeller pitch, it has been shown in connection with a reversible pitch propeller of the type forming the subject matter of Anderson application Serial No. 482,265, now abandoned, to which reference is made for a more detailed description of the propeller itself.

In general, movement of the pitch changing rod I2 will rotate cam I4 about a support I6 mounted on the engine nose I8 of the propeller driving engine. A pin 20 carried by support I6 and coacting with slot 22 in cam I4 will cause the cam to move axially toward and away from the propeller Ill as it is rotated in one direction or the other by movement of rod I2. The axial movement of the cam I4 actuates one part 24 of a follow-up valve, not shown, which, in turn,

`causes a change in propeller pitch in accord ance with the movements of part 24. Thus, for

each position of the rod l2 there is a corresponding pitch position of the propeller blades.

Referring now to Fig. l, the rod I2 is actuated in one direction by servo piston 26 of a servomotor, generally indicated at 25, and in the opposite direction by springs 28. One end of rod l2 adjacent the springs 28 carries a pair of pitchl limiting stops which will limit the movement of rod I2 and thus determine a low pitch position and a high pitch position for the propeller. As shown in Figs. 1, 3, and 4, these stops comprise nuts 36 and 32 carried on a threaded rod 34 mounted in an arm 36 secured to the end of rod I2. A stop pin 38 normally projects into the path of these nuts to limit the travel of the rod I2.

Pin 38 may, however, be retracted by actuation of a solenoid generally indicated at 40 so that the propeller may be placed in either feathered position by allowing nut 32 to pass the pin 38, or in reverse pitch position by allowing the nut 30 to pass the pin 38 as shown in Fig. 4. In practicing this invention, the nut 30 is adjusted so that the low pitch position is the blade position required at zero airspeed at the start of take off. This angle is usually between 15 and 35 at the reference blade station.

The servomotor 25 is controlled by a governor generally indicated at 42 and by three solenoid actuated valves A, B, and C Vshown in Fig. l in their cie-energized positions.

The governor is driven from the propeller driving engine through gear 44, by connections not shown, and comprises yballs 46 acting through valve sleeve 41 against adjustable Speeder spring 48. A pump 50 driven with the governor supplies iiuid under pressure in lines 52 and' 54. The pressure is regulated by a relief valve 56. Line 52 leads the pressure uid through valve ports 58 to th'interior of the valve sleeve 41. The flow of fluid through the valve sleeve 41 is controlled by the relative positions of the valve sleeve 4l and pilot valve 60. As has been previously indicated, the position of valve sleeve 41 is determined by the position of the fiyweights 46. The position of pilot valve 60 is determined by adjusting screw 60 and spring 62.

From the above description, it will be seen that when the governor speeds up and ilyballs 46 move outward and raise valve'sleeve 41, valve port 66 will move upward so that it is no longer covered by land 68 of pilot valve 60 thus opening conduit 'I0 to drain through passages l2 shown in Fig. 1, conduit 80 is blocked by a valve, generally indicated at 82 into which both con.` duits 10 and 80 lead. Conduit 10 is connectedk through valve 82 with conduit 84 and through solenoid actuated valve A with conduit 88 and thence with pressure chamber 88 of the servomotor 25. When the governor speeds up and conduit 10 is connected with drain, springs 28 will force servo piston 26 to the left as seen in Fig. l, the displaced fluid passing through'conduit 10 to drain. This movement of the servo piston 26 and of rod I2 will cause an increase.

in pitch of the propeller blades to thereby increase the load on the engine and restore the engine-propeller speed to 'the value preselected by the setting of the governor speeder spring. On the other hand, when the governor' yspeed falls below the preselected value, conduit f|will be connected with the pressure fluid in' line 52'32,

and will lead this iiuid to servomotor 25 forcing piston 28 to the right as seen in Fig. 1, and thereby causing a decrease in propeller pitch.

trolled thereby thus connecting pressure line 54 with servomotor 28, forcing piston 26 to the right to decrease the propeller pitch. After the propeller has assumed a reverse pitch position and has moved from the position indicated in Fig. 3 to that indicated in Fig. 4, switch handle 92 may be released to de-energize all of the solenoids and return the control of the servomotor 25 to the governor. Port 16 and land 18 of the governor 1o will then control the flow of pressure fluid in line 80 and thus control the flow of pressure fluid to and from servomotor 25 to maintain a constant propeller speed.

To return the propeller from the reverse pitch position to the position indicated in Fig. 1, switch handle 82 is moved to the right moving contact bar 84 to the left to close switches |02 and |04 thus energizing solenoids A and C. As before, solenoid A, when energized, disconnects the gov- 20 ernor from the servomotor. Solenoid C, when energized, opens the valve controlled thereby and A connects the servomotor with sump 14 through drain passages |08 and |08. Spring 28 will then return the servo valve and hence the propeller pitch to the normal forward pitch position and The above described operation of the governor, Y,

the servo valve, and the propeller is the normal operation when the propeller is in a forward pitch position. When the propeller is placed in a reverse pitch position and placed under control of the governor, it is necessary to move the lpropeller blades in a direction to increase the negative pitch when the speed is too great which is the exact reverse of the requirements when the prof peller is in its forward position.

In order to accomplish this reversal in the rei lation between the governor and the single acting servomotor, the reversing valve 82 is provided, which at the proper time will block of! conduit 'I0 and connect conduit 80 with the servomotor. As has been indicated above, movements of the yballs 46 produce exactly opposite results in conduits 'I0 and 80.

As shown in Fig. 1, valve 82 has a plunger 90 connected with piston26 to partake of the movements of that piston. As indicated in Fig. 3, the connections of conduits 10, 80. and 84 with valve 82 are arranged so that when the propeller blades are in zero pitch position, plunger 80 is about ready to change the connections so that a' further reduction in pitch will connectconduit 80 to conduit 84 and block conduit 10. The valve will then be in the position shown in Fig. 4 where the governor will be able to maintain constant speed by adjusting the pitch of the propeller when it is in its reverse pitch position.

In order to place the propeller in its reverse pitch position from the position indicated in Fig. 1, switch handle 92 is moved to the left, moving contact bar 04 to the right and closing switches 88, 98, and |00 to energize thereby solenoids A, B, and 40. Energizing solenoid 40 will withdraw stop pin 38 thus permitting the propeller to assume'a reverse position. Energizing solenoid A will close the valve controlled thereby thus disconnecting the governor from the servomotor 25. Energizing the solenoid B will open the valve conmove valve plunger to block conduit 80 and connect conduit 10 with conduit 84 at which time switch handle 82 may be released and the propeller control restored to the governor.

Fig. 5 shows a modification in which the valve 82 is actuated electrically in one direction by a solenoid H0 and may be spring pressed in the yother direction. In this modification a switch |2 which is actuated by cam ||3 is placed in a position to be actuated by movement of the rod |2 to close the switch as the propeller passes through the zero pitch position when changing from a forward to a reverse pitch, closing the switch H2, energizing solenoid ||0 and moving valve plunger to disconnect conduit 10 from conduit 84 and-connect conduit 80 with conduit 84. The connections between the governor and the servomotor will, therefore, be reversed as the propeller passes through the zero pitch position from a forward to a reverse pitch position. When control is returned to the governor, it will then maintain constant speed in the reversed pitch position. When the propeller blades pass through the 0 pitch position in changing pitch from a reverse pitch position to a forward pitch position switch ||2 will be opened, by a spring or its equivalent, and solenoid I |0 will be de-energlzed. Plunger '90 will then be returned, by a spring or its equivalent, to the position indicated in Fig. 5 wherel line k'lll is connected with line 84 and line 80 is blocked. Return of the control to the governor will then give constant speed governing in the forward pitch position.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

We claim:

1. In combination with a propeller having pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions, the propeller pitch being determined by the position of the pitch changing means, a governor connected with said pitch changing means for positioning said pitch changing means, and means actuated by said pitch changing means for reversing the connections betweenthe governor and the pitch changing means to reverse the action of the governor on said pitch changing means as the propeller changes from a forward to a reverse pitch position.

2. In combination with a propeller having pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions, the propeller pitch being determined by the position of the pitch changing means, a governor connected with said pitch changing means for positioning said pitch chang- .ing means, said governor having means for supplying power to one side of said pitch changing means to move said pitch changing means in one direction upon an increase in speed and having other means for supplying power to said one side of said pitch changing means to move said pitch changing means in said one direction upon a decrease in speed, and means actuated by said pitch changing means for changing the connection between the governor and the pitch changing means to disconnect one of said power supply means from, and connect the other of said power supplying means with said one side of said pitch changing means to reverse the action of the governor on said pitch changing means as the propeller changes from a forward to a reverse pitch position.

3, In combination with a propeller having pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions, the propeller pitch being determined by the position of the pitch changing means, a governor connected with said pitch changing means for positioning said pitch changing means, and means actuated by said pitch changing means for reversing the connections between the governor and the pitch changing means to reverse the action of the governor on said pitch changing means as the propeller passes through substantially zero pitch position.

4. In combination with a propeller having hydraulically actuated pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions, the propeller pitch being determined by the position of said hydraulically actuated pitch changing means', a governor connected with said pitch changing means for positioning said pitch changing means by controlling the how of hydraulic fluid to and from said pitch changing means, a valve and connections hydraulically connecting the governor and the pitch changing means, and means operatively connecting said valve and said pitch changing means to actuate said valve and reverse the action of the governor on said pitch changing means as the propeller changes its pitch direction.

5. In combination with a propeller having hydraulically actuated pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions, the propeller pitch being determined by the position of said hydraulically actuated pitch changing means, a governor connected with said pitch changing means for positioning said pitch changing means by controlling the ow of hydraulic fluid to and from said pitch changing means, a pair of conduits, said governor having means for connecting one conduit with hydraulic fluid under pressure upon an increase in speed and having other means for connecting the other c onduit with hydraulic fluid under pressure upon a decrease in speed and a valve connected with both said conduits and with one side of said pitch changing means and in one position connecting block said one conduit and connect said other conduit with said one side of said pitch changing l means to reverse the action of said governor on said pitch changing means as the ,propeller blades pass through substantially zero p'itch position.

6. In combination, a reversible, pitch propeller having forward pitch positions and reverse pitch positions, pitch control means forsaid propeller, a governor for controlling said pitch control means in both forward and reverse pitch positions to maintain the speed of the propeller substantially constant at a preselected value by increasing the propeller pitch upon an increase in speed when in forward pitch and by changing the pitch in the opposite direction upon an increase in speed when in reverse pitch, means, independent of said governor, for moving the pitch control means to change the propeller pitch between forward and reverse pitch positions, means actuated by said pitch control means for reversing the relation between the governor and said pitch control means so that the effect of the governor on said pitch control means when the propeller is in reverse pitch will be the opposite of the effect on said pitch control means when the propeller is in forward pitch.

7. In combination with a hydraulic propeller governor having two controlled ports one of which is connected with a source of fluid under pressure upon an increase in speed and the other of which is connected with a source of iiuid under pressure upon a decrease in speed, a valve, separate conduits leading from said ports to said valve, hydraulically actuated pitch controlling mechanism for said propeller including a pressure chamber, a single conduit connecting said valve with said pressure chamber, said valve in one positionl blocking one of said separate conduits and connecting the other of said separate conduits with said single conduit means operatively connecting said valve with said pitch controlling mechanism to move said valve to another position as the pitch changing mechanism passes a preselected position, said valve in said another position blocking said other separate conduit, and connecting,r said one of said separate conduits with said single conduit,

8. In combination, a propeller, pitch control means for said propeller, a hydraulic propeller governor having two controlled ports, one of which is connected with a source of fluid under pressure upon an increase in speed and the other of which is connected with a source of fluid under pressure upon a decrease in speed, a valve, separate conduits leading from said ports to said valve, a single conduit leading from said valve to the pitch control for said propeller, means operatively connecting said valve with said pitch control to move said valve and connect one or the other of said separate conduits with said single conduit in accordance with preselected positions of said pitch control.

9. Means for maintaining the speed of a reversible pitch propeller constant in both forward and reverse pitch positions comprising, pitch changing means including means hydraulically actuated in one direction and spring actuated in the other, means positioning the blades of said propeller in accordance with the position of said pitch changing means. a stop for limiting the extent of movement of said pitch changing means, means for withdrawing said stop, a governor having a pair of fluid controlling ports and means for connecting one port with fluid under pressure and the other port with drain when the governor speed is above a preselected value and for connecting said one port with drain and said other port with fluid under pressure when the governor speed is below a preselectedvalue, a control valve. separate conduits leading from said ports to said control valve, a solenoid actuated valve, a single conduit leading from said control valve to said solenoid actuated valve, a conduit leading from said solenoid actuated valve to said hydraulically actuated pitch changing means, a source of iiuid under pressure, a conduit leading from said source of fluid under pressure to said hydraulically actuated pitch changing means, another solenoid actuated valve located in said last-mentioned conduit, a drain, a conduit leading from said hydraulically actuated pitch changing means to said drain, a third solenoid actuated valve located in said last-mentioned conduit, means operatively connecting said control valve with said pitch changing means to position said control valve to connect one of `said separate conduits with said single conduit and block on the other oi' said separate conduits in all forward pitch positions of said propeller, means for simultaneously closing said rst mentioned solenoid actuated valve, opening said other solenoid actuated valve and withdrawing said stop to admit fluid under pressure to said hydraulically operated pitch changing means, placethe propeller in reverse Y- pitch position and move said control valve to block oil said one oi' said separate conduits and connect said other of said separate conduits with said single conduit, means for opening said ilrst mentioned solenoid actuated valve and closing said other solenoid actuated valve to restore control to said governor, whereby the governor may maintain the propeller speed constant in reverse pitch positions, means for simultaneously closing said first mentioned solenoid actuated valve, and

opening said third solenoid actuated valve tol drain said hydraulically actuated pitch changing means and place the propeller in forward pitch position and simultaneously move said control valve to restore the connection between said one of said separate conduits and said single conduit and block off the other separate conduit, whereby upon actuation of said means to restore controlV to said governor the governor may maintain the propeller speed constant in forward pitch position. f

versible pitch propeller constant in both forward and reverse pitch positions comprising, rpitch changing means including means hydraulically actuated in one direction and spring actuated in the other, means positioning the blades of said propeller in accordance with the position of said pitch changing means, a stop for limiting the extent of movement of said pitch changing means, means for withdrawing said stop, a governor having a pair of fluid controlling ports and means for connecting one port with fluid under pressure and the other port with drain when the governor speed is above a preselected value and for connecting said one port with drain and said other port with iluid under pressure when the governor speed is below a preselected value, a control valve, separate conduits leading from said ports to said control valve, a solenoid actuated valve a single conduit leading from said control valve to said 'f lically actuated means,

.55 l0. Means for maintaining the speed of a re-v solenoid actuated valve, a conduit leading from said solenoid actuated valve to said hydraulically actuated pitch changing means, a source of iluid under pressure, a conduit leading from said source of fluid under pressure to said hydraulically actuated pitch changing means, another solenoid actuated valve located in said last-mentioned conduit, means operatlvelyconnecting said control valve with said pitch changing means to position said control valve to connect one of said separate conduits with said single conduit and block oil.' the other oi' said separate conduits in all forward pitch positions of said propeller, means for simultaneously closing said first mentioned solenoid actuated valve, opening said other solenoid actuated valve and withdrawing said stop to admit fluid under pressure to said hydraulically operated pitch changing means, place the propeller in reverse pitch position and move said control valve to block 0R said one of said separate conduits and connect said other of said separate conduits with said single conduit, means for opening said rst mentioned solenoid actuated valve and closing said other solenoid actuated valve to restore control to said governor, whereby the governor may maintain the propeller speed constant in reverse pitch positions.

11. Means for maintaining the speed of a reversible pitch propeller constant in both forward and reverse pitch positions comprising, propeller pitch changing means, including means hydraulically actuated in at least one direction and means positioning the propeller blades in accordance with the position of said hydraulically actuated means, a governor having a pair of fluid controlling ports and means for connecting one port with fluid under pressure and the other port with drain when the governor speed is above a preselected value, a control valve, means for passing all the governor controlled uid through said control valve comprising separate conduits leading from said ports directly and only to said control valve, means hydraulically connecting said control valve with said hydraulically actuated means. means operatively connecting said control valve with said hydraulically actuated means to position said cpntrol valve to connect one of said separate conduits with said hydraumeans to actuate said pitch changing means to place said propeller in reverse pitch position, and means in said control valve. actuated by said pitch changing means to connect the other of said separate conduits with said hydraulically actuated means and block oil' said one conduit when the propeller is in reverse pitch position.

l2. Means for maintaining the speed of a revversible pitch propeller constant in both forward and reverse pitch positions comprising, `Propeller pitch changing means including means having an expansible chamber for receiving hydraulic iiuid and hydraulically actuated in at least one direction and means positioning the propeller blades in accordance with the position of said hydraulicallyconnecting said control valve with said pitch and reverse pitch positions comprising, pitch .\changing means including means having an expansible chamber for receiving hydraulic fluid and hydraulically actuated in at least one direction and means positioning the blades in accordance with the position of said hydraulically actuated means, a governor having a pair of uid controlling ports and means for connecting one port with fluid under pressure and the other port with drain when the governor speed is above a preselected value and for connecting said one port with drain and said other port with fluid under pressure when the governor speed is below a preselected value, a control valve, separate conduits leading from said ports to said control valve, means hydraulically connecting said valve with said chamber, electrically operated means, including a switch actuated by said pitch changing means, to position said control valve, said control valve connecting one of said separate conduits with said chamber when the propeller is in a forward pitch position, means to actuate said pitch changing means to place said propeller in reverse pitch position, said control valve being actuated by operation of said swltch in response to said pitch changing means to connect the other of said separate conduits with said chamber and disconnect said one conduit therefrom when the propeller is in reverse pitch position.

14. In combination with a propeller having pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions and whose pitch is determined by the position of the pitch changing means, a governor for positioning said pitch changing means, said governor having one means for supplying power to move said pitch changing means in one direction upon an increase in speed and having other means for supplying power to move said pitch changing means in said one direction upon a decrease in speed; means connecting said governor and said pitch changing means, and means including electrically operated. mechanism actuated by said pitch changing means for changing the connection of the governor with the pitch changing means to replace said one of said power supply means by the other of said power supply means to reverse the action of the governor on said pitch changing means as the propeller changes between forward and reverse pitch positions.

l5. In combination with a propeller having hydraulically actuated pitch changing means including means for changing the propeller pitch between forward and reverse pitch positions and whose pitch is determined by the position of said hydraulically actuated pitch changing means, a governor connected with said pitch changing means for positioning said pitch changing means by controlling the flow of hydraulic fluid to and from said pitch changing means, means connecting said governor and said pitch changing means, means for reversing the action of the governor on said pitch changing means as the 'propeller changes between forward and reverse pitch positions comprising a valve in the connection be.

tween the governor and the pitch changing means, and means, including a switch and a solenoid, operatively connecting said `valve and said pitch changing means and operated by movement of said pitch changing means to actuate said Valve.

16. In combination with a propeller having hydraulically actuated pitch changing means including means for changing the pitch between forward and reverse pitch, a governor connected with said pitch changing means for controlling the ow'of hydraulic fluid to and from one side of said pitch changing means, a pair of conduits, said governor having means for connecting one conduit with hydraulic iiuid under pressure uponA an increase in speed and having other means for connecting the other conduit with hydraulic uid under pressure upon a decrease in speed and a valve connecting said one conduit with said one side of said pitch changing means and blocking said other conduit, and means, including a switch operated by the pitch changing means, connected with electric power means for operating said valve to block said one conduit and connect said other conduit with said one side of said pitch changing means to reverse the action of said governor on said pitch changing means as the propeller blades pass through substantially zero pitch position.

17. In combination with a propeller having hydraulically actuated pitch changing means lncluding means for changing the pitch between forward and reverse pitch, a governor connected with one side of said pitch changing means for positioning said pitch changing means by controlling the ow of hydraulic fluid to and from said one side of said pitch changing means, means connecting both of said devices with said one side of said pitch changing means including a valve in the connection between the governor and said one side of said pitch changingmeans selectively connecting either of said devices with said one side and blocking the other device, and means mechanically connecting said valve and said pitch changing means to actuate said valve and reverse the action of the governor on said pitch changing means by switching from one to the other of said devices as the propeller changes from a forward to a reverse pitch position.

18. Means for maintaining the speed of a reversible pitch propeller constant in both forward connecting one port with fluid under pressure and the other port with the drain when the governor speed is above a preselected value and for connecting said one port with drain and said other port with fluid under pressure when the governor speed is below a preselected value, a control valve, separate conduits leading from said ports to said control valve, an electrically actuated valve, a single conduit leading from said control valve to said electrically actuated valve, a conduit leading from said electrically actuated valve to said hydraulically actuated pitch changing means, a source of fluid under pressure, a conduit leading from said source of `fluid under pressure to said hydraulically actuated pitch changing means, another electrically actuated valve located in said last-mentioned conduit, means operatively connecting said control valve with said pitch changing means to position said control valve to connect one of said separateconduits with said single conduit and block oi'f the other of said separate conduits in all forward pitch positions of said propeller, means for simultaneously closing said first-mentioned electrically actuated valve and opening said other electrically actuated -valve to admit iluid under pressure to said hydraulically operated pitch changing means, place the propeller in reverse pitch position and move said control valve to block ofi said one of said separate conduits and connect said other of said separate conduits with said single conduit, means for opening said first-mentioned electrically actuated valve and closing said other electrically actuated valve to restore control to said governor whereby the governor may maintain the propeller speed constant in reverse pitch positions.

19. Means for maintaining the speed of a reversible pitch propeller constant in both forward and reverse pitch positions comprising, pitch changing means including means hydraulically actuated in one direction, a governor having a pair of fluid controlling ports and means for connecting one port with fluid under pressure and the other port with drain when the governor 'speed is above a preselected value and for connecting said one port with drain and said other port with fluid under pressure when the governor 'speed is below said preselected value, a control valve, separate4 conduits leading from said ports to said control valve, a single conduit connecting said control valve and said hydraulically actuated pitch changing means, a selectively actuated valve in said single conduit, a source of iluid under pressure, a conduit connecting said source of fluid under pressure and said hydraulically actuated pitch changing means, another selectively actuated valve located in said lastmentioned conduit, said control valve connecting one of said separate conduits with said single conduit, means for simultaneously closing said ilrst-mentioned selectively actuated valve and thereby blocking all hydraulic connection between said governor and said pitch changing means and opening said other selectively actuated valve to admit fluid to said pitch changing means and reverse the propeller pitch, means movable with said pitch changing means for moving said control valve upon movement of the propeller to reverse pitch, to disconnect said one separate conduit from and connect said other separate conduit with, said single conduit, means for restoring control to said governor with the propeller in the reverse pitch position.

20. Means'for maintaining the speed 4of a reversible pitch propeller constant in both forward and reverse pitch positions comprising, propeller pitch changing means, including hydraulically actuated means for positioning the propeller blades, a source of hydraulic pressure, means connecting said source with said hydraulically actuated means including, a governor controlling the ilow of hydraulic fluid between said source and said hydraulically actuated means to vary the propeller pitch and control the propeller speed,

means for actuating said pitch changing means to move the propeller blades between forward and reverse pitch positions, a reversing control valve located in said connecting means between said governor and said hydraulically actuated means and operatably connected with said pitch changing means and movable with said blades as they pass through zero pitch to reverse the controlling action of said governor on said hydraulically actuated means.

21. In combination with a reversible controllable pitch propeller. a governor for controlling the propeller speed by varying the propeller pitch, means connecting said governor with said propeller, means for changing said connecting means to reverse the action of said governor on said propeller, means for reversing the propeller pitch, and means responsive to propeller pitch changing movement for actuating said changing means to reverse the action of said-governor on said propeller when the propeller reaches a predetermined pitch position.

22. In combination with a reversible controllable pitch propeller, a governor for controlling the .propeller speed by varying the propeller pitch,

means operatively connecting said governor with said propeller, means for changing said connecting means to reverse the action of said governor on said propeller, manually controlled means for reversing the propeller pitch, and means responsive to pitch changing movement for actuating said changing means.

23. In combination with a propeller havinga blades and blade pitch changing means, a speed `responsive governor operatively connected with said pitch changing means and positioning said blades to maintain the propeller speed substantially constant, manually controlled means for changing the blade pitch including means for changing the pitch in either direction between forward and reverse pitch, and means positioned in accordance with the blade pitch and operatively associated with the connection between said governor and said pitch changing means including means to reverse the pitch changing eiect of said governor by changing the connection between said governor and said pitch changing means as the blade pitch changes in either direction between forward and reverse pitch.

ERLE MARTIN.

MURRAY C. BEEBE, Jn.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,216,416 Mader Oct. l, 1940 2,228,776 Mullen Jan. 14, 1941 2,293,912 Mullen Aug. 25, 1942 2,307,849 Mullen Jan. 12, 1943 2,320,195 Rindeisch May 25, 1943 2,343,416 Keller Mar. 7, 1944 2,378,938 McCoy June 26, 1945

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